1. Field of the Invention
The present invention relates to an intermediate transfer drum for an electro-photographic process, which is suitably applied to a printing apparatus or an image forming apparatus employing an electro-photographic process such as a laser printer, an electro-photographic copying machine or the like, particularly applied to a color printing apparatus or a color image forming apparatus employing an electro-photographic process, and an image forming apparatus using the same.
2. Related Art Statement
In a color printing apparatus or a color image forming apparatus employing an electro-photographic process, the systems for carrying out putting colors one upon another using a plurality of colors of toner include various systems such as one for carrying out putting colors one upon another on a photosensitive body, one for carrying rout that on a sheet of paper, one for carrying out that on an intermediate transfer body or the like.
In the system for carrying out putting colors one upon another on a photosensitive body out of the above-described systems, since it is necessary to carry out exposing again from the top of a toner image formed on the photosensitive body, the toner image formed already becomes disordered or the like, resulting in a great defect of image quality formed.
On the other hand, in the system for carrying out putting colors one upon another on a sheet of paper, with respect to the system for carrying out putting colors one upon another on an intermediate transfer body, which requires two transfers such that a primary transfer is carried out from the photosensitive body to the intermediate transfer body, and a secondary transfer is carried out from the intermediate transfer body to a sheet of paper, one time transfer will suffice, and therefore, the above-described system has been heretofore used generally, and has been employed for various color copying machines.
On the other hand, the system for carrying out putting colors one upon another on an intermediate transfer body, which has been considered to be disadvantageous in terms of image quality, has been employed for a color printer or the like whose image quality is not so much demanded, in which the intermediate transfer body has a belt shape, and making use of advantages such that the space efficiency within the printing device, or corresponding properties of paper such as cardboard are excellent.
As the forms of the above-described intermediate transfer body, a belt shape, a drum shape or the like are considered, but as the intermediate transfer body of the drum shape (hereinafter referred to as an intermediate transfer drum), generally, use is made of one in which a rubber belt is put on the outer circumferential surface of a metal drum.
In the intermediate transfer drum as described, when a slip occurs between the rubber belt and the metal drum, a deviation of color occurs in an image formed, or the rubber belt becomes twisted and levitates, resulting in defective transfer, and irregular transfer.
Particularly, where there is not equipped with means for driving the intermediate transfer drum, when the photosensitive body is driven, a great load is applied to the surface of the intermediate transfer drum. Further, even where there is equipped with means for driving the intermediate transfer drum at a speed equal to that of the photosensitive body, where there is equipped with a blade cleaning means for cleaning the surface of the intermediate transfer drum, a great load is applied to the surface of the intermediate transfer drum by the contact of the blade therewith. And, due to such a load as described, a slip or deviation becomes occurred between the rubber belt and the metal drum.
From the foregoing, there is generally employed the procedure wherein when the rubber belt is put on the outer circumferential surface of the metal drum, an adhesive is poured into and between the outer circumferential surface of the metal drum and the inner circumferential surface of the rubber belt so as not to generate a slip between the rubber belt and the metal drum.
However, in the procedure as described above, unless the adhesive is uniformly coated, the surface of the intermediate transfer drum becomes rugged so that irregular transfer occurs, because of which the yield of the intermediate transfer drum cannot be enhanced, making it difficult to achieve mass production. Further, when reuse of the metal drum or the rubber belt is taken into consideration, if the metal drum and the rubber belt are bonded together, they cannot be separated easily, greatly impairing the reuse.
The present invention has been accomplished in view of the conventional a problems noted above with respect to the intermediate transfer drum in which the rubber belt is put on the outer circumferential surface of the metal drum. It is an object of the invention to provide an intermediate transfer drum and an image forming apparatus using the same, in which even if a great load is applied to the surface of the intermediate transfer drum, no slip occurs between the rubber belt and the metal drum, and there occurs no phenomenon such that in an image formed, deviation of color occurs, or the rubber belt becomes twisted and levitated, resulting in defective transfer or irregular transfer.
It is another object of the invention to provide an intermediate transfer drum and an image forming apparatus using the same, in which without employing the procedure for pouring an adhesive into and between the outer circumferential surface of the metal drum and the inner circumferential surface of the rubber belt, the yield of the intermediate transfer drum to enable facilitating mass production, and the metal drum and the rubber belt can be separated easily so as to enable reusing them.
For achieving the aforementioned objects, the intermediate transfer drum according to the present invention is characterized in that assuming that the rubber hardness of the rubber belt is not more than 80xc2x0 , the ratio between the outside diameter R (mm) of the metal drum and the inside diameter r (mm) of the rubber belt is P. and 100% tensile stress of the rubber belt is f1 (kgf/cm2), then f1xc3x97(Pxe2x88x921)xc2x15 results, and the permanent elongation in the actual using state of the rubber belt is set to 10% or less.